Photocatalytic property correlated with microstructural evolution of the biochar/ZnO composites

Abstract

The ZnO composite photocatalyst has recently been an effective tool for the removal of organic pollutants during water treatment. However, it is still a great challenge to fabricate cost-effective ZnO composite photocatalyst with high photocatalytic efficiency. This study presents the synthesis of the composites, biochar-supported ZnO nanoparticles, by adjusting the molar ratio of biochar/ZnO with hydrothermal method. The composite, biochar-supported 3D flower-shaped ZnO nanoparticles with a preferred crystal plane (002), exhibited the excellent degradation efficiency of methylene blue (MB) under UV–visible light when the molar ratio of biochar/ZnO is 1:0.5. The chemical bond Zn–O–C formed at the interface between the biochar and ZnO nanoparticles, and this facilitates a lower recombination rate of the e−/h+ pairs originated from the stimulation of ZnO nanoparticles, which was also supported by the results of transient photocurrent response and the electrochemical impedance spectroscopy (EIS). The synergetic effect of biochar and ZnO consequently lead to the higher degradation efficiency of the composite than that of pure ZnO. Moreover, trapping experiments further confirmed the contribution of the active radicals (h+, •O2-, OH•) in the degradation of MB. In addition, the essential role of porous biochar with a high specific surface in the cooperatively catalytic mechanism was also discussed in detail. This research offers a revealing insight into the design and fabrication of ZnO photocatalysts that applied in the purification and remedy of environment.

Keywords

• Biochar
• 3D flower-shaped ZnO nanoparticles
• UV–Visible light
• Synergetic effect
• Photocatalytic activity